There’s not much concrete data I can find on accident rates on highways vs non-highways. You would expect small side streets accidents to have lower fatality rates though, with wrecks at highway speeds to have much higher fatality rates. From what I see, a government investigation into how safe autopilot is determined there were 13 deaths, which is very low number given the billions of miles driven with autopilot on (3 billion+ in 2020, probably 5-10billion now? Just guessing here since I can’t find a newer number).
But yeah, there are so many factors with driving that it’s hard get an exact idea. Rural roads have the highest fatality rates (making up to 90% of accident fatalities in some states), and it’s not hard to image that Tesla’s are less popular in rural communities (although they seem to be pretty popular where I live).
But also rural roads are a perfect use case for autopilot, generally easy driving conditions where most deaths happen due to speeding and the driver not paying attention. Increased adoption of self driving cars in rural communities would probably save a lot of lives.